MACHINE READABLE RECORDS

Updated: Monday, March 31, 1997

Over the years, records have been produced in a variety of
shapes, sizes, and types. Whether records are hand-copied ledger
books or printed text, information can be read simply by looking
at the text. Records on audio, video, and computer media present
an important change in the way information is recorded and
retrieved. Such records require equipment to read the information
they hold. These records are referred to as machine
readable.

The information stored on a videotape or computer diskette
must be retrieved by a machine specifically designed to read its
particular format. The format encompasses both the
physical media and the way the electronic signals are recorded on
that media. VHS format videotapes require a video
player designed to read the particular format of those VHS tapes.
(For example, a video produced in England would not be playable
on a standard video player purchased in the U.S.) Audiocassettes
can only be played on a cassette player that accommodates the
correct size audiotape that includes the correct number of tracks
in the correct physical location.

Changes in technology can cause machine formats to become
obsolete, preventing access to information even if the medium (e.g.,
tape, diskette, CD) holding the information is in perfect
condition. Machine readable records are also sensitive to their
environment, making environmental controls a requirement. Machine
readable records cannot be stored in an attic or basement and
reclaimed after years of neglect.

It is important to know what machine readable records you are
storing. For audiotapes, include the record name, format type,
playing speed, and the date that the copy was made in inventories
and on storage containers or on the item itself. Also include any
special signal processing that may have been used, such as
"Dolby C" for noise reduction.

For computer tapes and diskettes, record and maintain
information about the version of the operating system and version
number of the program or application used to create the record,
as well as ownership and date of each record series. Be sure to
mark media in the manner recommended by the manufacturer, e.g.,
never use ballpoint pen for marking CD's.

Audiotape, videotape, and computer diskettes are sometimes
called magnetic media, because information is recorded on
magnetized particles. Because magnetic heads record the
information, magnets can also erase it or make it hard to read.
For this reason, do not expose these media to strong magnetic
fields, e.g., electric motors or audio speakers.

Dust, heat, and high relative humidity are the enemies of
machine readable records. Dust scratches tape surfaces, obscuring
information and clogging the magnetic heads used to read them.
Heat may cause the plastic film of the tape to distort, changing
the recorded pattern and scrambling information. Heat can also
deform plastic parts inside a cassette, preventing the tape from
moving from one reel to the other. High relative humidity can
degrade the binder that holds the magnetic information particles
on the tape and encourage mold to grow.

For these reasons, store machine readable records in an
environment free from heat and dust. Ideal long-term storage
conditions would be very cool and dry (50o
F and 20% RH). While such conditions may not be realistic for
your setting, do not let temperatures exceed 70o F,
and if possible, keep the relative humidity below 40%. Make every
effort to keep temperature and relative humidity levels constant.

CARE AND HANDLING

Avoid touching the surface of any tape or computer diskette.
Oil from skin leaves a residue that can coat the equipment's
playing head and attract dust. If you must handle tape, wear
clean white cotton gloves. Never use commercial products
advertised to clean tapes and diskettes. Contact an experienced
professional to clean or repair dirty or damaged tapes.

Return tapes and diskettes to their individual boxes
immediately after use to avoid possible damage and dust. Never
use paper clips or adhesive tape to attach notes directly to
cassettes, reels, or diskettes.

Always rewind tapes before storing. If a tape is only
partially played, advance the tape to the end (using either
regular speed or fast-forward) before rewinding it for storage.

Maintain machines according to manufacturer's specifications
to ensure that equipment will not damage tapes.

Most compact disks or CD's are not magnetic media. However,
CD's do require careful handling to ensure access to information
that has been recorded on the bottom (printless) side of the
disk. CD's have been advertised as almost indestructible. They
are not. Scratches to the surface can distort the laser light
that reads the disk, causing it to skip or repeat tracks. Remove
dust with a soft cloth, wiping from the center out, as if along
the spokes of a wheel. Return CD's to their cases immediately
after use.

USE AND BACKUP COPIES

Backup copies are the best insurance for
protecting valuable tapes. In the event of media
aging or a natural disaster, a copy may be the only means
available to retrieve information from a master that is no longer
playable. To prevent the loss of information, create a "copy
master" from the original tape. Use this copy master only
when making another use copy.

Use reel to reel audio tape for master audio copies. A written
transcript of an audio or video tape can also be used as a
"use copy" or "backup copy." A transcript may
contain every word on the original tape, or only a general
rendering of the discussion.

The loss of a single computer diskette can mean the loss of a
large quantity of information. For this reason, backup copies are
critical to ensuring the preservation of computer-based records.
If maintaining an active computer database of records is part of
an institutional operation, copy the information recorded on the
system's hard drive onto backup diskettes or tapes on a daily
basis. As a part of disaster prevention, store backup copies in
another secure location.

REFRESHING

Audio, video, and computer tapes designed to be maintained for
long periods of time will require periodic copying to ensure
access to information. Every three to five years, re-copy all
master tapes onto high quality, polyester-based tape in the
currently established format for the media.

MIGRATION

Information formats disappear as new technology emerges.
Within the last twenty years, 8-track tapes, beta format video,
1/2" videotape, and countless other formats have become
obsolete. Access to information is limited when machines
necessary to read these records fail and cannot be replaced. To
ensure access to information, copy older formats onto a stable
technology while playback machines remain available.

Be knowledgeable about the formats of all machine readable
records in your care.

RESOURCES AND PUBLICATIONS

Machine readable technologies provide versatile methods for
recording and storing information beyond the capability of
conventional paper-based records. However, machine readable
records require a proactive response from their custodians to
ensure the long-term preservation of information.

For more information on preserving machine readable records,
phone 404-656-3554 to contact the Conservator at the Georgia
Department of Archives and History, a division of the Office of
Secretary of State.

Kenney, Anne and Stephen Chapman. Digital Imaging
for Libraries and Archives. Ithaca, NY:
Cornell University, 1996. This is an expanded version of a
training manual used in digital imaging training at Cornell.

Lindner, Jim. Digitization Reconsidered.
This and a number of other related publications are available at http://www.panix.com/~vidipax,
or from the author by phoning Vidipax at 212-982-5676. The
Vidipax help line is 1-800-653-8434.

Van Bogart, John W.C. Magnetic Tape Storage and
Handling, A Guide for Libraries and Archives. Washington,
DC: The Commission on Preservation and Access and the National
Media Laboratory, 1995 ,Telephone: 202-939-3400

[The Georgia Department of Archives and History wishes to
thank Mr. Jim Lindner for his technical assistance in the
preparation of this leaflet.]